Chemical Bonds/Transcript
Transcript Text reads: The Mysteries of Life with Tim & Moby. An animation shows a car moving through an automatic car wash. The view changes to the exit from the car wash where a man, Tim, is watching the cars come out. After a blue car comes out, the next thing to come out is a robot, Moby. Moby is on all fours and is sparkling clean. Moby stands up, shakes off some water, and moves next to Tim. Moby has four blue lights on his chest. Tim is wearing a white T-shirt. In the center is a drawing of two intersecting circles. Each circle contains a white plus sign in a red background. There are two negative symbols where the two circles intersect. Tim is holding a sheet of paper. Water can be heard dripping off of Moby. TIM: All done? MOBY: Beep. Tim reads from a letter. TIM: Dear Tim & Moby, How do hydrogen and oxygen stick together to make water? Atomic glue or something? From, Tabitha. Moby brings his hand up to his mouth and tries to stifle a laugh. MOBY: Beep. TIM: Actually, she’s not that far off! Atoms do tend to stick together, almost as if they were glued. If they didn’t, there wouldn’t be any visible stuff— Tim’s body is now composed of lots of small, colored circles. His voice becomes more and more disjointed. TIM: just a bunch of microscopic atoms floating around by themselves. Tim looks at himself as he becomes solid again. TIM: Whoa. TIM: But atoms like to stick together, and the reason has to do with what’s inside them. An animation shows colored spheres moving around and some come together and then stick to each other. MOBY: Beep? TIM: Atoms are made up of three basic particles: positively-charged protons; negatively-charged electrons; and neutrons, which have no charge. An animation shows a diagram of an atom. In the center are yellow and orange spheres clumped together. Around this nucleus are three circular bands containing blue spheres, representing electrons. The innermost band has two electrons. The next band has eight electrons. The outermost band has 18 electrons. As Tim refers to the positively-charged protons, plus signs appear on the orange spheres. At the mention of the negatively-charged electrons, minus signs appear on the blue spheres. When Tim refers to the neutrons, the yellow spheres in the nucleus are highlighted. TIM: Protons and neutrons clump together in the center of an atom, forming its nucleus. The nucleus is outlined in red. TIM: Electrons whizz around the nucleus at different distances, which we call shells. The animation now shows the electrons circling the nucleus. MOBY: Beep? TIM: Oh, shells aren't really perfect circles—this is just a simple model. In reality, electrons orbit the nucleus in three-dimensional patterns called clouds. The animation shows the circular orbits rotating to become three-dimensional. Soon, they turn into clouds. TIM: But the circular model helps us see that each shell can hold a certain number of electrons. The first shell, closest to the nucleus, can hold two. The animation reverts back to the two-dimensional image showing three shells. The innermost shell is highlighted in red and the two blue spheres are numbered “1” and “2.” TIM: The second shell can hold eight electrons, while the third shell can hold up to 18, and so on. The second shell is briefly highlighted and its electrons are numbered from 1 to 8. Then the third shell is highlighted and its electrons are numbered from 1 to 18. The scene shifts back to Tim and Moby. TIM: And this is where things get… sticky. Heh. Sticky. MOBY: Beep? TIM: The number of electrons in an atom's outermost shell control how reactive, or likely to bond, it is. An animation shows a close-up of an atom with two electrons. The nucleus is labeled “Upper H e.” Superimposed on the nucleus is a happy face. Yellow cartoon hands are gripping the band that the electrons are on. A caption reads: “reactive.” TIM: When the outer shell is completely full, the atom is inert, meaning it will resist bonding. An oxygen atom (nucleus labeled “Upper O”) approaches the helium atom. The oxygen atom also is displayed with a cartoon caricature. The oxygen atom has two electrons in the inner shell and six electrons in the outer shell. Two empty white circles appear in the outer shell. The cartoon-like image shows the oxygen atom’s hands grabbing for the two electrons circling the helium nucleus; but the hands belonging to the helium atom fend them off. A caption reads: “inert.” The helium atom’s mouth animates into a frown and he speaks in a squeaky voice. HELIUM ATOM: Get lost! The scene shifts back to a close up of Tim speaking. TIM: Eight electrons is another stable pattern, even in shells that can hold way more. A picture of the periodic table of elements is shown. The squares comprising the table are filled with the abbreviations for the names of the elements, starting with “Upper H” and extending to “Upper A c.” The right-most column in the table is highlighted in green and contains six elements. Their abbreviations are “Upper H e, Upper N e, Upper A r, Upper K r, Upper X e,” and “Upper R n.” A caption reads: “noble gases.” Below the table, three atoms are shown, each with a smiley face drawn on the nucleus. The first one is labeled “Upper H e” and has one shell containing two electrons. The second one is labeled “Upper N e” and has two shells. The inner shell holds two electrons and the second shell holds eight electrons. The third atom is labeled “Upper A r” and has three shells. The shells hold two, eight, and eight electrons going from inner to outer shell respectively. TIM: In all of the noble gases, the outer shell is either full or has eight electrons. That's why they almost never form bonds. The other elements on the table tend to occur in molecules: sets of two or more atoms bonded together. A diagram of a molecule appears. In the center is an atom with a nucleus labeled “Upper O”. It has two shells. The inner shell has two electrons and the outer shell has eight electrons. Attached to it on the left is an atom with a nucleus labeled “Upper H” and a single shell containing two electrons. The circle representing the shell of this hydrogen atom is tangent to the circle representing the outer shell of the oxygen atom. There are two electrons shown to lie on both of these circles. Another such hydrogen atom is attached to the oxygen atom on the right and its two electrons are also shared with the oxygen atom. A caption reads: “molecules.” MOBY: Beep? TIM: It helps to think of atoms as wanting to be inert. An animation shows an atom labeled “Upper N a” with a frown on its face. It has three shells. The inner shell holds two electrons. The middle shell holds eight electrons. The outer shell holds one electron but has seven empty circles also along the shell. TIM: So they try to gain or lose electrons to reach a stable number. The outer shell (including its electron and the seven empty circles) disappears and the mouth on the cartoon nucleus changes from a frown to a smile. MOBY: Beep? TIM: Well, take water. It’s made of two hydrogen atoms and one oxygen atom. A new animation shows an oxygen atom (labeled “Upper O”) in the center and two hydrogen atoms (each labeled “Upper H”) on either side of it. The oxygen atom has two shells. The inner one contains two electrons and the outer shell contains six electrons and two empty circles. Each hydrogen atom has one shell consisting of a lone electron and an empty circle. All three atoms have frowns on their cartoon faces. TIM: As you can see, hydrogen has one electron in its outermost shell. The electrons orbiting the hydrogen atoms are highlighted. The screens shifts back to Tim and Moby sanding side by side, Tim speaking. TIM: It would love to have one more, since two electrons would fill that shell up. Oxygen has six electrons in its outer shell; since the second shell can hold eight electrons, oxygen is looking for two more. The screen returns to the previous animation with one oxygen atom and two hydrogen atoms, and the six electrons around the outer shell of oxygen are highlighted. TIM: So, oxygen shares a pair of electrons with one hydrogen, and another pair of electrons with another hydrogen. The two hydrogen atoms get closer to the central oxygen atom and the circles representing their shells touch and then the portion of the shell where the electrons are located superimpose the circle representing the outer shell of the oxygen atom. They now share two electrons with the oxygen atom. The animation shows the circles for the shells of the hydrogen atoms each having two electrons. The outer shell of the oxygen atom now has eight electrons. All three atoms are now smiling. TIM: Now all three atoms are stable. LEFT HYDROGEN ATOM: Yay! RIGHT HYDROGEN ATOM: Yay! OXYGEN ATOM: Yay! TIM: This sharing of electron pairs is called a covalent bond. The scene shifts back to Tim and Moby. MOBY: Beep? TIM: Nope, that’s not the only way atoms stick together. Ionic bonds happen when one atom takes an electron from another. An animation shows an unhappy orange atom on the left side of the screen with three shells. There is one electron, represented by a blue dot and seven other open circles along the outermost shell. A green atom is depicted on the right side of the screen. The green atom appears forlorn and has seven electrons in its outer shell with one empty slot for another electron. The animated hand of the green atom reaches over and grabs the electron from the orange atom’s outer shell and puts it in its empty slot. The third and outermost shell of the orange atoms disappears. The orange atom looks confused. GREEN ATOM: Yoinkers! TIM: The extra electron gives the first atom a negative charge. A minus sign appears on the brow of the green atom. TIM: And the other atom becomes positively charged, since it lost an electron. A plus sign appears on the brow of the orange atom. TIM: In other words, they both become ions—atoms with electrical charges. And since opposite charges attract, they bond together! The animation shows a red heart appearing between the two atoms with flashing lines surrounding each atom. The atoms move closer together and hold hands. Both atoms are now smiling. The orange atom is labeled “Upper N a plus” and the green atom is labeled “Upper C l minus.” TIM: This is called electrostatic attraction. Sodium chloride—which is just table salt—is held together by ionic bonds. MOBY: Beep? Moby is seen holding some salt in his left hand. He throws the salt over his left shoulder. Tim is then shown standing next to Moby, talking. TIM: That’s a good point. On their own, sodium and chlorine atoms have totally different properties than salt. Sodium is a soft metal that burns the skin and explodes on contact with water. A dish containing six small chunks of metal is shown. A hand holding an eyedropper comes into view. One drop of water falls from the eyedropper and lands in the dish. Several of the chunks of metal burst into flames. TIM: And chlorine is a poisonous green gas! A beaker is shown containing a green gas. Affixed to the beaker is a sticker bearing the picture of a skull and crossbones. TIM: But when these two elements react, they form an ionic bond, and we get an edible crystal! A drawing of a saltshaker is shown, half filled with salt. Next to it is a mound of salt. MOBY: Beep. TIM: Yup, covalent bonds can change an atom’s properties, too. Hydrogen and oxygen are both invisible gases, and hydrogen is explosive! An animation shows two beakers, one is labeled “Upper H” and the other is labeled “Upper O.” A hand appears with a lit match and moves the match over the neck of the hydrogen beaker. A small exposition occurs. TIM: But when they react, they form water, a very stable liquid. A beaker containing a liquid is labeled “Upper H subscript 2 Upper O.” A match gets tossed in and lands in the liquid. The flame on the match is extinguished. The scene returns to Tim speaking. TIM: If you break that covalent bond with a little electricity, you get hydrogen and oxygen gas again. The scene shifts to Moby outside the car wash. MOBY: Beep. Moby extends his finger and a blue light starts to form around it and grow. TIM: No, wait! Tim grabs Moby’s arm and the light disappears. TIM: Ya know? Every week, it’s the same thing: I teach you something cool, you shoot a laser beam out your finger, and I get in trouble. Well, not this time. Moby appears to be unhappy. MOBY: Beep. TIM: I’m gonna pretend I didn’t hear that. Category:BrainPOP Transcripts Category:BrainPOP Science Transcripts